Modifying landing mat material properties may decrease peak contact forces but increase forefoot forces in gymnastics landings

This study investigated how changes in the material properties of a landing mat could minimise ground reaction forces (GRF) and internal loading on a gymnast during landing. A multi-layer model of a gymnastics competition landing mat and a subject-specific seven-link wobbling mass model of a gymnast were developed to address this aim. Landing mat properties (stiffness and damping) were optimised using a Simplex algorithm to minimise GRF and internal loading. The optimisation of the landing mat parameters was characterised by minimal changes to the mat's stiffness ( < 0.5%) but increased damping (272%) compared to the competition landing mat. Changes to the landing mat resulted in reduced peak vertical and horizontal GRF and reduced bone bending moments in the shank and thigh compared to a matching simulation. Peak bone bending moments within the thigh and shank were reduced by 6% from 321.5 Nm to 302.5 Nm and GRF by 12% from 8626 N to 7552 N when compared to a matching simulation. The reduction in these forces may help to reduce the risk of bone fracture injury associated with a single landing and reduce the risk of a chronic injury such as a stress fracture.     

Money matters: The impact of prize money on doping behaviour

In professional sports, the amounts disbursed in rank-based prize money distributions decline sharply, and differences in performance are extremely small. This disparity may provide a high incentive for doping. Due to the complexity of doping, obtaining meaningful insights on the influence of prize money distribution and the pecuniary value of prize money on doping behaviour of elite athletes using game theory or other approaches has not been possible. The authors perform a computerised social simulation through agent-based modelling to analyse doping behaviour in competitive sport. The results show that the distribution of prize money in particular has an enormous impact on the prevalence of doping. By contrast, the total amount of prize money is less decisive for doping behaviour. Further, doping costs are observed to have only a marginal effect on doping prevalence, depending on the tested prize money distribution and its amount. The simulation results can be used by sports federations and competition organisers who should distribute the prize money more evenly to all athletes to reduce doping.     

体育传播对青少年的负面影响及对策

最早的时候体育运动是一种比较纯净的活动,人们确实崇尚奥林匹克精神,而那个时候体育传播业还不发达,人们对体育运动的了解多是通过报纸和电影纪录片,看到的也多是“洁本”的体育记录。而随着体育热潮的逐年增高,报纸、杂志、电台、电视、网络等宣传媒体中的“体育园地”不断扩     

武汉市妇女弱势群体对健身项目的选择及其影响因素

运用文献资料法、问卷调查法、数理统计法与逻辑分析法等方法,对武汉市妇女弱势群体（工人、离退休、下岗、家庭妇女四种群体）进行健身项目选择与影响因素进行调查研究。结论：武汉市妇女弱势群体参与体育锻炼以直接参与为主;在年龄上以青年和老年居多;文化程度偏低;身体状况较差;锻炼项目选择比较单一但群体性比较强;体育消费支出少;信息获取渠道单一;所接受的健身方面的指导较少。结合影响其参与锻炼的因素,提出有针对性的建议,为武汉市妇女弱势群体的健身提供参考。     

Effects of a resistance-training programme on endoplasmic reticulum unfolded protein response and mitochondrial functions in PBMCs from elderly subjects

Abstract

Aging has been related with a decline in the ability to handle protein folding, which leads to endoplasmic reticulum stress and alterations in unfolded protein response (UPR). Importantly, physical activity could activate the UPR and attenuate or prevent age-induced endoplasmic reticulum (ER) dysfunction. The current study evaluated the effects of a resistance exercise on UPR and mitochondrial functions in peripheral blood mononuclear cells (PBMCs) from elderly subjects. Thirty healthy women and men (age, 72.8, s_x??=?2.2 years) were randomized to a training group, which performed an 8-week resistance training programme, or a control group, which followed their daily routines. The phosphorylation of PERK and IRE1, as well as ATF4, and XBP1 protein expression, significantly increased following the training, while expression of BiP, AFT6 and CHOP remain without changes. Additionally, the intervention also induced an increase in PGC-1α and Mfn1 protein levels, while no changes were found in Drp1 expression. Finally, the resistance protocol was not able to activate PINK1/Parkin and Bnip3/Nix pathways. The results obtained seem to indicate that 8-week resistance exercise activates the UPR, stimulates mitochondrial biogenesis, maintains mitochondrial dynamics and prevents mitophagy activation by unfolded proteins in PBMCs from elderly subjects.     

Experimental and finite element analysis of a tennis ball impact on a rigid surface

An explicit finite-element (FE) model of a pressurised tennis ball is presented. The FE model was used to model an oblique impact between a tennis ball and a rigid tennis surface, to further the understanding of this impact. Impacts were also conducted in the laboratory and the results from the FE model were in good agreement with this experimental data. The FE model was used to illustrate why a tennis ball rebounds with a higher vertical coefficient of restitution in an oblique impact compared to an equivalent impact perpendicular to the surface; this equivalent perpendicular impact has the same inbound velocity as the vertical component of the oblique impact. The FE model was also used to illustrate that the structural compliance of the felt covering on a tennis ball was a contributing factor to the ball attaining more spin in the impact than would have been calculated using a conventional analytical model. Also, the spin values calculated in the FE simulation were in good agreement with experimental data.     

新疆回族女性体育锻炼状况及影响因素的调查研究

对新疆回族集中地昌吉州、伊犁州及焉耆县各年龄段的回族女性参加体育锻炼状况进行调查,结果表明：回族女性参与体育锻炼状况不容乐观;回族女性总体体育锻炼意识不强,参与体育锻炼的积极性不高且影响因素较多。     

Effects of treadmill running and fatigue on impact acceleration in distance running

The effects of treadmill running on impact acceleration were examined together with the interaction between running surface and runner's fatigue state. Twenty recreational runners (11 men and 9 women) ran overground and on a treadmill (at 4.0 m/s) before and after a fatigue protocol consisting of a 30-minute run at 85% of individual maximal aerobic speed. Impact accelerations were analysed using two lightweight capacitive uniaxial accelerometers. A two-way repeated-measure analysis of variance showed that, in the pre-fatigue condition, the treadmill running decreased head and tibial peak impact accelerations and impact rates (the rate of change of acceleration), but no significant difference was observed between the two surfaces in shock attenuation. There was no significant difference in acceleration parameters between the two surfaces in the post-fatigue condition. There was a significant interaction between surface (treadmill and overground) and fatigue state (pre-fatigue and post-fatigue). In particular, fatigue when running overground decreased impact acceleration severity, but it had no such effect when running on the treadmill. The effects of treadmill running and the interaction need to be taken into account when interpreting the results of studies that use a treadmill in their experimental protocols, and when prescribing physical exercise.     

Effects of antisocial behaviour on opponent's anger,attention, and performance

Sledging, which is verbal antisocial behaviour in sport, aims to impair an opponent’s performance. Previously, variations in performance have been attributed to changes in emotion and cognition. To improve our understanding of sledging, the current experiment examined the effects of verbal antisocial behaviour on anger, attention and performance. Participants performed a competitive basketball free-throw shooting task under insult (verbal behaviour designed to offend and upset the performer), distraction (verbal behaviour designed to draw attention away from the task), or control (neutral verbal behaviour) conditions. Performance was assessed by the number of successful baskets and a points-based scoring system, while anger and attention were measured post-task. The insult condition provoked more anger than the control and distraction conditions, whereas the insult and distraction conditions increased distraction and reduced self-focus compared to the control condition. Although verbal antisocial behaviour had no overall direct effect on performance, mediation analysis showed that anger indirectly impaired performance via distraction. Implications for the antisocial behaviour-performance relationship are discussed.     

Expectancy effects in tennis: The impact of opponents' pre-match non-verbal behaviour on male tennis players

Abstract

In this study, we examined the impact of a male opponent's pre-match body language and clothing (general vs. sports-specific) on how his performances were judged by an observer. Forty male tennis players viewed videos of a male target tennis player warming up and then observed playing footage of the target. Each participant viewed the target player warming up displaying one of four combinations of body language and clothing (positive body language/tennis-specific clothing; positive body language/general sportswear; negative body language/tennis-specific clothing; negative body language/general sportswear). Participants rated the performance of the tennis player and gave their perceptions of the likely outcome of a tennis match with the target player. Analyses of variance indicated that clothing and body language had an interactive effect on both outcome expectations and ratings of performance. The findings support the contention that the initial impressions athletes form of their opponents can influence the way in which they judge the performances of opponents and their perceived likelihood of success against the same opponents.     

Effects of structural components of artificial turf on the transmission of impacts in football players

The third generation of artificial turf systems (ATS) has matched the mechanical behaviour of natural grass, but today a high heterogeneity at structural level and mechanical behaviour in the new ATS also exists. The objective was to analyse the effect of the structural components of ATS football pitches and running speed on the capacity of impact attenuation. A total of 12 athletes were evaluated at three speed conditions (3.33 m/s, 4 m/s and maximum speed) on four different ATS, classifying them by their components (length of fibre, type of in-fill and sub-base). Impact attenuation was significantly higher in ATS3, characterised by longer fibre compared to other ATS with less fibre length. The ATS4 with a higher length fibre and built on compacted granular material proportioned significantly lower values in the maximum peaks of tibia acceleration. Finally, as speed increases, the peak tibia impacts were significantly higher. Longer fibre length and the capacity to accommodate a higher quantity of infill facilitate higher impact attenuation. Equally, a compacted granular sub-base is related to lower magnitude of maximum tibia peaks. Finally, the magnitude of the tibia acceleration peaks is dependent of running speed for all ATS analysed, being higher as speed increases.     

乒乓球拍微结构对乒乓球与球拍碰撞过程的研究

利用商用有限元软件MSC．MARC,通过对乒乓球与球拍碰撞过程的数值模拟,着重研究由传统木材和碳纤维复合材料板叠合而成的乒乓球拍的微结构对碰撞后乒乓球运动规律的影响,为优化设计新型球拍提供理论依据。     

The influence of shaft stiffness on potential energy and puck speed during wrist and slap shots in ice hockey

The purpose of this study was to explore the relationship between hockey stick shaft stiffness and puck speed with mechanical energy considerations during stationary wrist and slap shots. Thirty left-handed pro-model composite hockey sticks, submitted by eleven hockey stick manufacturers, were subjected to a mechanical cantilever bend test to determine the shaft stiffness of each stick. Eight sticks representing the entire spectrum of stiffnesses were then used by five elite male hockey players to perform stationary wrist and slap shots in a laboratory setting. Eight infra-red high-speed digital video cameras were used to capture shaft deformation and puck speed. A second mechanical test then replicated the loading patterns applied to each stick during shooting. Force-deformation data from this test were used to determine the shaft stiffness and potential energy storage and return associated with each stick during shooting. The results of this study suggest that shaft stiffness has an influence on puck speed in wrist but not slap shots. During a wrist shot, a given player should realise higher puck speeds with a stick in which they store increased elastic potential energy in the shaft. In general, flexible sticks were found to store the most energy. However, how the athlete loads the stick has as much influence on puck speed as stick construction. Energy considerations were unable to explain changes in puck speed for the slap shot. For this type of shot it is the athlete and not the equipment influencing puck speed, but the governing mechanisms have yet to be elucidated.     

24 h Accelerometry: impact of sleep-screening methods on estimates of sedentary behaviour and physical activity while awake

Although accelerometers can assess sleep and activity over 24 h, sleep data must be removed before physical activity and sedentary time can be examined appropriately. We compared the effect of 6 different sleep-scoring rules on physical activity and sedentary time. Activity and sleep were obtained by accelerometry (ActiGraph GT3X) over 7 days in 291 children (51.3% overweight or obese) aged 4–8.9 years. Three methods removed sleep using individualised time filters and two methods applied standard time filters to remove sleep each day (9 pm–6 am, 12 am–6 am). The final method did not remove sleep but simply defined non-wear as at least 60 min of consecutive zeros over the 24-h period. Different methods of removing sleep from 24-h data markedly affect estimates of sedentary time, yielding values ranging from 556 to 1145 min/day. Estimates of non-wear time (33–193 min), wear time (736–1337 min) and counts per minute (384–658) also showed considerable variation. By contrast, estimates of moderate-to-vigorous activity (MVPA) were similar, varying by less than 1 min/day. Different scoring methods to remove sleep from 24-h accelerometry data do not affect measures of MVPA, whereas estimates of counts per minute and sedentary time depend considerably on which technique is used.     

六合八法拳对中老年人健康的影响

文章从六合八法拳对中老年人运动系统、心血管系统、呼吸系统、神经系统、消化系统、免疫力系统的影响等六个方面详细论述了六合八法拳对中老年人健康的影响。分析认为：六合八法拳是一个优秀的独具风格的拳种,具有较高的健身价值、实用价值和研究价值,对六合八法拳的挖掘整理和研究,将会为中华武术宝库增添新的内容,丰富中老年人的健身项目,为21世纪人类健康长寿做出贡献。     

振动波方向、频率对振动训练的影响

研究不同方向的振动波、振动频率在振动训练中对肌肉力量的影响。通过对人体在负重蹲练习时附加不同振动方向、振动频率的振动刺激,测量训练前后等速肌力矩峰值、功率等指标。经对测量数据对比分析发现,水平方向和多维方向振动波的训练效果要优于垂直方向;在15～45Hz振动频率范围内,振动训练的效果有明显增加的趋势。振动训练采用水平或多维方向的振动波,以及振动频率大于30Hz时,可收到较好训练效果。     

Effects of purposeful soccer heading on circulating small extracellular vesicle concentration and cargo

BackgroundConsidering the potential cumulative effects of repetitive head impact (HI) exposure, we need sensitive biomarkers to track short- and long-term effects. Circulating small extracellular vesicles (sEVs) (<200 nm) traffic biological molecules throughout the body and may have diagnostic value as biomarkers for disease. The purpose of this study was to identify the microRNA (miRNA) profile in circulating sEVs derived from human plasma following repetitive HI exposure.MethodsHealthy adult (aged 18–35 years) soccer players were randomly assigned to one of 3 groups: the HI group performed 10 standing headers, the leg impact group performed 10 soccer ball trapping maneuvers over 10 min, and the control group did not participate in any soccer drills. Plasma was collected before testing and 24 h afterward, and sEVs were isolated and characterized via nanoparticle tracking analysis. Next-generation sequencing was utilized to identify candidate miRNAs isolated from sEVs, and candidate microRNAs were analyzed via quantitative polymerase chain reaction. In silico target prediction was performed using TargetScan (Version 7.0; targetscan.org) and miRWalk (http://mirwalk.umm.uni-heidelberg.de/) programs, and target validation was performed using luciferase reporter vectors with a miR-7844-5p mimic in human embryonic kidney (HEK) 293T/17 cells.ResultsPlasma sEV concentration and size were not affected across time and group following repetitive HI exposure. After 24 h, the HI read count from next-generation sequencing showed a 4-fold or greater increase in miR-92b-5p, miR-423-5p, and miR-24-3p and a 3-fold or greater decrease in miR-7844-5p, miR-144-5p, miR-221-5p, and miR-22-3p. Analysis of quantitative polymerase chain reaction revealed that leg impact did not alter the candidate miRNA levels. To our knowledge, miR-7844-5p is a previously unknown miRNA. We identified 8 miR-7844-5p mRNA targets: protein phosphatase 1 regulatory inhibitor subunit 1B (PPP1R1B), LIM and senescent cell antigen-like domains 1 (LIMS1), autophagy-related 12 (ATG12), microtubule-associated protein 1 light chain 3 beta (MAP1LC3B), integrin subunit alpha-1 (ITGA1), mitogen-activated protein kinase 1 (MAPK1), glycogen synthase kinase 3β (GSK3β), and mitogen-activated protein kinase 8 (MAPK8).ConclusionCollectively, these data indicate repetitive HI exposure alters plasma sEV miRNA content, but not sEV size or number. Furthermore, for the first time we demonstrate that previously unknown miR-7844-5p targets mRNAs known to be involved in mitochondrial apoptosis, autophagy regulation, mood disorders, and neurodegenerative disease.     

奥林匹克运动与旅游——兼谈2008年奥运会对浙江体育旅游的影响

通过奥运与体育旅游的关系及浙江体育旅游的现状分析，认为2008年北京奥运会能促进浙江体育旅游业的快速发展，有利于浙江投资环境的改善，扩大就业机会，带动产业结构的调整和社会经济的协调发展；并为2008年奥运会对浙江体育旅游业的发展要求提供策略，促进浙江体育旅游持续、稳定、健康的发展。     

Effects of emphasising opposition and cooperation on collective movement behaviour during football small-sided games

ABSTRACT

Optimizing collective behaviour helps to increase performance in mutual tasks. In team sports settings, the small-sided games (SSG) have been used as key context tools to stress out the players’ awareness about their in-game required behaviours. Research has mostly described these behaviours when confronting teams have the same number of players, disregarding the frequent situations of low and high inequality. This study compared the players’ positioning dynamics when manipulating the number of opponents and teammates during professional and amateur football SSG. The participants played 4v3, 4v5 and 4v7 games, where one team was confronted with low-superiority, low- and high-inferiority situations, and their opponents with low-, medium- and high-cooperation situations. Positional data were used to calculate effective playing space and distances from each player to team centroid, opponent team centroid and nearest opponent. Outcomes suggested that increasing the number of opponents in professional teams resulted in moderate/large decrease in approximate entropy (ApEn) values to both distance to team and opponent team centroid (i.e., the variables present higher regularity/predictability pattern). In low-cooperation game scenarios, the ApEn in amateurs’ tactical variables presented a moderate/large increase. The professional teams presented an increase in the distance to nearest opponent with the increase of the cooperation level. Increasing the number of opponents was effective to overemphasise the need to use local information in the positioning decision-making process from professionals. Conversely, amateur still rely on external informational feedback. Increasing the cooperation promoted more regularity in spatial organisation in amateurs and emphasise their players’ local perceptions.